[unreadable] Hearing deficits are the third leading cause of disability in the aged. Over half of all people in the US over seventy suffer some form of age-related hearing deficits. This is a ubiquitous problem with many sources, and the peripheral contributions to age-related deficits, particularly high frequency hearing loss, have been explored and have revealed several important features of these disorders. However, there remains relatively little understood about the consequences of age-related hearing loss and normal aging on central auditory structures, particularly the neocortex, and how age-related changes in either anatomical or physiological processes in central structures give rise to perceptual deficits. Our lack of understanding of these central effects is due in large part to the lack of an effective animal model that (1) shares many organizational features of auditory cortex with humans, (2) has a reasonably long life span such that age-related hearing deficits progress over the course of several years as in the human, and (3) are not prohibitively expensive. I have a unique opportunity to develop such an animal model as I have access to a large geriatric colony of macaque monkeys that satisfy these three criteria. The goals of this proposal are to determine which auditory cortical response properties are most influenced by normal aging and age-related hearing loss. Two normal young animals, two older animals with age- related high frequency hearing loss, and two older age-matched animals without age-related hearing loss will be used in these experiments. Spectral, spatial, and temporal response properties of single neurons in primary and secondary auditory cortical fields will be defined in each, monkey. Comparisons between neurons in different monkeys, as well as in auditory cortical fields that have been reorganized due to the high frequency hearing loss, will be compared to determine which aspects of auditory information processing are most susceptible to aging and age-related hearing loss. The results of this study will provide the foundation for future research programs aimed at the development of remedial treatments and therapies, as well as in hearing aid design, for individuals suffering from age-related hearing deficits. [unreadable] [unreadable]